This invention relates to an apparatus and method for treating a fluid stream. More particularly, but not by way of limitation, this invention relates to an apparatus and method for removing contaminants, such as oil, from an effluent.
In the oil and gas industry, the production of oil and gas from subterranean reservoirs entails the production of insitu waters. Separation of the three phases (namely: oil, gas and water) is necessary for proper handling. The process of separating the produced water is complicated and costly. Government regulations require that the separated water contain only trace amounts of contaminants such as oil. Once properly separated, the water requires suitable disposal.
The production facilities may be located in remote areas and/or in offshore waters. Many prior art devices have been designed to separate the oil and water. Even water that has been separated in a prior art separators may contain small amounts (100 to 2,000 mg/L) of suspended hydrocarbons in oil droplet form. The physical diameters of the oil particles may be very small.
Stokes Law describes the buoyant rise velocity of an oil droplet in a water-continuous phase. It has been shown that the larger the size of an oil droplet, the greater its vertical velocity. A common prior art device used for treatment equipment is a water skimmer tank. This type of tank is designed to provide large residence times during which coalescence and gravity separation can occur. This type of separator is usually used in combination with other types of devices such as three-phase separators.
Other types of devices have been useful in separating fine oil particles from water. One technique has been to use the gas flotation device. One such device is seen in U.S. Pat. No. 4,800,025 entitled "APPARATUS AND PROCESS FOR THE GAS FLOTATION PURIFICATION OF OIL-CONTAMINATED WATER" and assigned to applicant; nevertheless, while this gas flotation device is very useful, there remains a need for an improved apparatus for separating oil and water. For instance, operators will use various other separating devices to more completely separate the oil from the water. However, in the remote areas where space is a critical factor, the physical placement of said devices causes problems. Operators attempt to minimize the amount of equipment while at the same time maximize the separation efficiency.
Therefore, there is a need for a device that will increase the efficiency of contaminated effluent separation. There is also a need for a system that will separate an oil-water mixture that minimizes space. Other needs will be met by the teachings and disclosures of this invention, as will be more fully understood by a reading of the following description.